Abstract: A method of maintaining photolithographic precision alignment for a wafer after being bonded, wherein two cavities are formed at the rear surface of a top wafer at the position corresponding to alignment marks made on a bottom wafer. The depth of both cavities is deeper than that of a final membrane structure. The top wafer is then bonded to the bottom wafer which already has alignment marks and a microstructure. This bonded wafer is annealed to intensify its bonding strength. After that, a thinning process is applied until the thickness of the top wafer is reduced to thinner than the cavity depth such that the alignment marks are emerged in the top wafer cavities thereby serving as alignment marks for any exposure equipment.

Abstract: A measurement method for the thinned thickness of the silicon wafer, wherein thickness inspection patterns are fabricated onto the silicon wafer substrate by anisotropic etching, and then the wafer is polished with a polisher; thus a wafer with desired thickness can be obtained after the polish is proceeded; the thickness of the upper wafer is determined by the said inspection patterns, then the wafer is sorted by thickness; thus it can be applied to the MEMS micromachined devices that in need of the wafer with such precise thickness.

Abstract: A method of maintaining photolithographic precision alignment for a wafer after being bonded, wherein two cavities are formed at the rear surface of a top wafer at the position corresponding to alignment marks made on a bottom wafer. The depth of both cavities is deeper than that of a final membrane structure. The top wafer is then bonded to the bottom wafer which already has alignment marks and a microstructure. This bonded wafer is annealed to intensify its bonding strength. After that, a thinning process is applied until the thickness of the top wafer is reduced to thinner than the cavity depth such that the alignment marks are emerged in the top wafer cavities thereby serving as alignment marks for any exposure equipment.

Abstract: A measurement method for the thinned thickness of the silicon wafer, wherein thickness inspection patterns are fabricated onto the silicon wafer substrate by anisotropic etching, and then the wafer is polished with a polisher; thus a wafer with desired thickness can be obtained after the polish is proceeded; the thickness of the upper wafer is determined by the said inspection patterns, then the wafer is sorted by thickness; thus it can be applied to the MEMS micromachined devices that in need of the wafer with such precise thickness.